"He just thought it was something that would be humorous," she told The Sydney Morning Herald, adding that the member of staff had no idea it would spark thousands of comments on Twitter and be picked up by news outlets in the US and Europe.

Ford said the worker would face an internal review for the stunt, but was unlikely to be reprimanded.

"We are hoping it just does blow over," she said.

Ford said the library could not move Armstrong's books into another category without first receiving instructions from the Libraries Australia governing body.

Manly Council, which runs the library, has reportedly been inundated with calls relating to the sign.

In a much-anticipated interview with US talk show queen Oprah Winfrey, Lance Armstrong admitted for the first time that an array of performance-enhancing drugs helped sweep him to a record seven Tour de France titles from 1999-2005.

Years of aggressive denials - including vitriolic attacks on those who questioned him, collapsed last year when he was stripped of his Tour titles and banned for life by the US Anti-Doping Agency.